Cryogenic x-ray detectors

Silicon drift detectors (SDDS) for K-d

The antikaon-nucleon (KbarN) interaction close to threshold provides crucial information of the interplay between spontaneous and explicit chiral symmetry breaking in low-energy QCD. In this context the importance of the kaonic deuterium X-ray spectroscopy has been well recognized, but no experimental results were obtained up to now due to the difficulty of the measurement.

For this purpose we plan to use new SDD chips, which were developed in collaboration by Fondazione Bruno Kessler – FBK and Politecnico di Milano in Italy.

Monolithic arrays with 9 detector segments with a total area of 5.76 cm2 are perfectly suited for the proposed experiment.  For these SDDs special preamplifier chips (CUBE), were developed.

First test measurements were performed successfully. For example an stability test running for 72 hours, performed at a SDD temperature of 120 K, achieved an energy resolution of 130 eV (close to the theoretical limit) at 6 keV. The drift time at this working temperature is around 200 ns. Further cooling of the SDDs below 50 K will allow a further reduction of the drift time below 100 ns.

The design of the target detector setup is shown below, which is planned to be used for the K-d experiment at J-PARC (Japan Proton Accelerator Research Complex). The cryogenic target filled with deuterium is running at a temperature of ~ 25K, while the SDDs surrounding the target cell will work at 40 K.